This invention relates to a hydraulically operated loader vehicle for transferring bulk material from one location to another, including a weighing system for weighing each load handled by the loader and for accumulating the total weight of the material transferred; and to a method for weighing bulk material during such transfer by a loading vehicle.
This invention is concerned with the use of loading machines, commonly referred to as front end loaders, for the loading of bulk material such as gravel from ground stock piles onto transport vehicles such as railroad cars or trucks. It is important that these vehicles be loaded to maximum legal capacity for a number of reasons. In the case of railroad cars, when the cars are underloaded, such underloading simply represents loss of gross sales when railroad cars are in short supply because the shipper is simply not utilizing the shipping capacity which is available. If a car is overloaded, and this is not discovered until the car is weighed in the railroad yard, the cost of reducing the load is very expensive in terms of man hours and equipment; and, in addition, the material unloaded is either lost or can only be marketed at greatly reduced value.
In the case of transport trucks, the penalty for underloading is the same as that for railroad cars; and the penalty for overloading includes fines and possible loss of material which must be unloaded. It is important then that means be provided for loading vehicles accurately so that they can be loaded near legal capacity with minimum risk of overloading.
While experienced loader operators may be able to estimate very closely the loads which are being loaded onto a transport truck or railroad car, this is only possible where the loader operator is able to visually observe the load in the bucket, and has the experience to estimate the weight of the particular material which is being loaded. It is a fact, however, that for many large capacity loaders, the load in the bucket is not visible to the operator; and it is necessary therefore to provide some form of automatic system for weighing each bucket load and, preferably, to accumulate the weights of the several bucket loads which are loaded onto the transport vehicle.
A principal object of this invention is to provide a weighing system and method for use with hydraulic loading apparatus, to enable the loading of a transport vehicle to maximum capacity without overload.
Another object of this invention is to provide a system and method for the precision weighing of bulk materials loaded from a stockpile onto a transport vehicle, while the material is being loaded.
A further object of this invention is to provide a system and method for the precision weighing of each bucket load transferred to another location.
Still another object of this invention is to provide a hydraulic loader having a self-contained system for weighing each bucket load, and for accumulating the weight of a series of bucket loads which are transferred to another location.
A still further object of this invention is to provide a weighing system and method for a hydraulic loader, for weighing bulk material loaded onto a transport vehicle efficiently with minimum loss of operator time.
These objects are accomplished in a weight measuring and indicating system for a loader having at least one hydraulic lift cylinder for elevating a load carrier. The system includes a transducer, for operative connection to a lift cylinder, for detecting instantaneous hydraulic pressure therein and for producing an instantaneous electric analog signal responsive to the instantaneous hydraulic pressure. A converter coupled to the output of said transducer converts the analog signal to a frequency signal which consists of pulses generated at a frequency proportional to the analog signal. A counter, for counting and displaying the output pulses of the converter, is controlled by gate means coupling the counter to the converter. A clock means coupled to the gate means controls the passing of converter output pulses to the counter, whereby the counter display will indicate the load in the loader carrier.
In more detail, an add switch is also coupled to the gate means for further controlling the passage of converter output pulses to the counter, whereby the counter functions as an accumulator counter responsive to operation of the add switch.
In other detail, the system includes means for monitoring either the analog input to the converter or the pulse frequency output of the converter for indication of the instantaneous carrier load.
In still other detail, the loader includes a frame, and lift arms elevated by the lift cylinder which pivotally support the load carrier. Coacting indicator members mounted respectively on the frame and on the lift arm, and visible to the loader operator, indicate to the operator a selected elevated weigh position of the lift arms relative to the frame.
These objects are accomplished in a method which includes the steps: detecting the instantaneous pressure in the loader hydraulic lift cylinder; converting the instantaneous pressure to an electric analog signal proportional to the instantaneous pressure; adjusting the analog signal to eliminate the component which represents the weight of the load carrier of the loading vehicle; converting the adjusted analog signal to a frequency signal consisting of pulses generated at a frequency proportional to the adjusted analog signal; and passing the frequency signal to a pulse counter, through control gate means, for counting and displaying pulses representing the instantaneous carrier load.
In further detail the method includes the steps: positioning the load carrier in a preselected weigh position relative to the vehicle frame; and operating the control gate means for each carrier load only when the carrier is in the weigh position.
In still more detail the method involves passing the frequency signal to a second counter through the same control gate means, and passing a control signal to said second counter through second gate means to accumulate the pulses representative of successive carrier loads.
The novel features and the advantages of the invention as well as additional objects thereof, will be understood more fully from the following description when read in connection with the accompanying drawings.